| dc.description.abstract | Two indoor feeding trials were conducted to investigate the effects of dietary superdosing of
Quantum Blue® phytase on the growth performance, as well as mineral and amino acid
utilization of juvenile channel catfish (initial weight of 8.02 ± 0.18 g) and red drum (initial
weight of 4.99 ± 0.09 g) over 8 and 9 weeks, respectively. Both feeding trials had a negative
control diet formulated to contain adequate nutrients but deficient in available phosphorus based
on the established requirement of each species. Another four diets were produced from the
negative control formulation with Quantum Blue® phytase supplemented at either 1000, 2000,
4000, or 8000 FTU/kg dry diet. A positive control diet also was prepared with supplemental
monocalcium phosphate (MCP) to meet the available phosphorus requirement of each species.
Both channel catfish and red drum fed the phytase-supplemented diets had significantly (P <
0.05) improved weight gain and feed efficiency compared to fish fed the negative control diet. In
addition, dietary phytase supplementation significantly enhanced bone concentrations and whole-body retention of various minerals, although slightly differences were found between the two
species. Furthermore, dietary phytase supplementation significantly increased apparent
availability of phosphorus from the posterior intestinal region, and reduced excretion of nitrogen
and various minerals. Additionally, apparent digestibility coefficients (ADCs) for most
indispensable and dispensable amino acids were promoted by dietary phytase. Based on
regression analysis of weight gain data from channel catfish and red drum feeding trials, the optimal dietary phytase dosage was estimated to be 5,492⁵⁰⁵⁰∕₅₇₇₃ and 5,520⁵¹⁵⁰∕₆₁₇₅ FTU phytase /kg of dry diet, respectively.
In addition, a pond feeding trial was carried out with channel catfish (initial weight of 39.8
± 3.46 g) reared in cages to evaluate the effect of dietary phytase supplementation of a
commercial diet and the interaction between dietary MCP and phytase supplementation. The
results shown that neither dietary MCP nor phytase supplementation increased growth
performance of channel catfish when the diet had adequate available phosphorus. Besides that,
although both dietary MCP and phytase supplementation increased bone concentration of some
minerals, only dietary phytase supplementation increased the retention of these minerals. | |
